Early Molecular and Cytogenic Response Is Predictive for Long-Term Progression-Free and Overall Survival in Chronic Myeloid Leukemia (CML) Hanfstein B et al. Leukemia 2012;[Epub ahead of print]. Hanfstein B et al. Proc ASH 2011;Abstract 783.

Background The advent of second-generation tyrosine kinase inhibitors (TKIs) in the front-line treatment setting of chronic myeloid leukemia (CML) has prompted a closer evaluation of the response to imatinib (N Engl J Med 2010;362:2251, 2260). Early assessment of response markers might identify slow responders harboring a BCR-ABL positive clone with an inferior susceptibility to TKIs. Slow responders could benefit from an early dose escalation or a change of treatment to a second-generation TKI, thus avoiding the risk of disease progression. Current study objective: Evaluate the impact of molecular and cytogenetic response levels after 3 months of an imatinib-based treatment on the course of CML. Hanfstein B et al. Leukemia 2012;[Epub ahead of print].

CML Study IV Methods Patients with CML treated with imatinib (n = 1,303). Patients were randomly assigned to receive: –Imatinib 400 mg/d –Imatinib 400 mg/d + interferon alpha (IFN) –Imatinib 400 mg/d + low-dose cytarabine (arm closed 2005) –Imatinib 400 mg/d after IFN failure (arm closed 2005) –Imatinib 800 mg/d Molecular and cytogenetic responses analyzed at 3 months and 6 months. BCR-ABL and total ABL transcript levels were measured by quantitative RT-PCR, standardized according to international scale (BCR-ABL IS ). Cytogenetic response was determined by conventional metaphase analyses with standard G-banding or fluorescence R-banding techniques. Endpoints include progression-free survival (PFS) and overall survival (OS). Hanfstein B et al. Leukemia 2012;[Epub ahead of print].

PFS by Molecular Response BCR-ABL IS at 3 months Five-year PFSp-value ≤1% (n = 218)96% NS — >1%-10% (n = 281)92% >10% (n = 189)87% — BCR-ABL IS at 6 months Five-year PFSp-value ≤1% (n = 498)96% — >1%-10% (n = 194)89% NS >10% (n = 91)86% — NS = not significant PFS was defined as the absence of accelerated phase, blast crisis and death. Probability of PFS was calculated from the Kaplan-Meier plot and compared by log-rank statistics. Hanfstein B et al. Leukemia 2012;[Epub ahead of print].

PFS by Cytogenetic Response Ph+ at 3 months Five-year PFSp-value ≤35% (n = 336)94% >35% (n = 122)87% Ph+ at 6 months Five-year PFSp-value 0% (n = 319)97% >0% (n = 160)91% Hanfstein B et al. Leukemia 2012;[Epub ahead of print]. Median proportion of Philadelphia chromosome-positive metaphases (Ph+) = 8%

OS by Molecular Response BCR-ABL IS at 3 months Five-year OS p-value ≤1% (n = 218)97% NS — >1%-10% (n = 283)94% >10% (n = 191)87% — BCR-ABL IS at 6 months Five-year OS p-value ≤1% (n = 498)97% — >1%-10% (n = 196)90% NS >10% (n = 95)88% — OS was defined as the absence of death from any cause. Probability of OS was calculated from the Kaplan-Meier plot and compared by log- rank statistics. Hanfstein B et al. Leukemia 2012;[Epub ahead of print].

OS by Cytogenetic Response Ph+ at 3 months Five-year OSp-value ≤35% (n = 336)95% >35% (n = 124)87% Ph+ at 6 months Five-year OSp-value 0% (n = 320)97% >0% (n = 162)91% Hanfstein B et al. Leukemia 2012;[Epub ahead of print].

Author Conclusions The levels of molecular or cytogenetic response at 3 months of imatinib treatment allow for a risk stratification of patient outcome in terms of PFS and OS. Patients (28%) who failed to achieve 10% BCR-ABL IS level at 3 months had a 5-year OS of only 87%. Survival rates were significantly better for patients with >1% to 10% and ≤1% BCR-ABL IS. However, there was no significant difference between the >1% to 10% and ≤1% BCR-ABL IS groups. Therefore, missing the 10% BCR-ABL IS landmark at 3 months predicts inferior survival. A similar risk group is defined by failure to achieve the 35% Ph+ landmark at 3 months: –5-year OS with Ph+ >35% at 3 months is 87%. Treatment optimization is suggested for patients missing these landmarks. Hanfstein B et al. Leukemia 2012;[Epub ahead of print].

Investigator Commentary: Molecular and Cytogenetic Response After 3 Months of Imatinib Treatment Predicts Survival in CML This study reported a significant difference in outcome for patients with CML depending on molecular and cytogenetic responses after 3 months of imatinib treatment. After 3 months of therapy, it is possible to predict the risk of disease progression and death. Results from this study raised the question as to whether a patient’s treatment should be changed early on, depending on the response after 3 months of imatinib therapy. Clinical studies have already been initiated based on these results, in which early use of a different TKI has been attempted to improve outcomes in patients with CML in chronic phase. Second-generation TKIs like dasatinib and nilotinib have received FDA approval in the front-line setting for CML. Although this study suggests the administration of a different second-generation TKI as first-line therapy for patients who will not fare well on imatinib, the question of how such patients will be predefined remains unanswered. Overall, monitoring of molecular and cytogenetic responses to therapy early on may help community oncologists in treatment decision-making. Interview with Srdan Verstovsek, MD, PhD, January 25, 2012